1. Field of the Invention
This invention relates to detecting abnormal pressure conditions upstream and downstream of a medicament pump having a pressurized source of fluid. More particularly, this invention is capable of indicating abnormal pressure conditions including: source overpressurization upstream of the pump and occlusion of the outlet tube downstream from the pump.
2. Description of Related Art
Medicament pumps, such as, the peristaltic pump disclosed in commonly assigned U.S. Pat. No. 4,576,556, which is incorporated herein by reference, are well known in the prior art and have wide application in the medical field. A typical application for such a pump is implanting the pump within a patient""s body for treating a neurodegenerative disease or trauma, as is disclosed in commonly assigned U.S. Pat. No. 5,711,316, which is incorporated herein by reference. Other applications are also well known. The term xe2x80x9cmedicament pumpxe2x80x9d as used herein, refers to any device for delivering medicaments and having a pressurized reservoir, including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like.
Such a medicament pump will typically be coupled to a pressurized fluid source via an inlet tube and will typically administer medication or another fluid via a catheter coupled to the pump outlet via a pump outlet tube. A shortcoming of such pumps is their inability to detect, and provide an indication of, abnormal pressure conditions upstream and downstream of the pump. For instance, neither abnormally high upstream pressure, which could indicate reservoir overpressurization during reservoir refilling, nor abnormally high downstream pressure, which could indicate catheter occlusion, are detected by known prior art pumps having pressurized sources.
As certain therapies, which use a medicament pump, progress beyond treatment for pain and spasticity, immediate detection of potential catheter occlusion states, which could prevent drug delivery, is desirable. This is especially desirable for therapies which do not provide an immediate feedback as a clinical sign that interruption in therapy has occurred, for instance, therapies for Amyotrophic Lateral Sclerosis, Parkinson""s Disease, and Alzheimer""s Disease.
In addition, while the pressurized source of medication is being refilled, overfilling can cause source overpressurization, which can cause a pump to malfunction and could produce catastrophic results. Known prior art medicament pumps that have pressurized sources typically use a shut-off valve to mechanically close during the refill process to prevent reservoir overpressurization. Such mechanical valves tend to require close tolerances in order to optimize both reservoir volume and overpressurization protection, thereby undesirably increasing the complexity of fabrication of such reservoirs. In addition, such mechanical shut-off valves do not provide any indication that the source has been overfilled, or that the source is overpressurized.
The prior art fails to address these problems. For instance, U.S. Pat. No. 4,468,219 issued to George et al. (""219 patent) discloses a pump flow rate compensation system that speeds up a peristaltic pump motor in response to sensing that a transition from positive pump inlet pressure to a negative pump inlet pressure has occurred. The ""219 patent does not disclose monitoring the downstream pressure, detection of abnormally high upstream or downstream pressures, or detection of an abnormal difference between downstream and upstream pressures.
U.S. Pat. No. 4,690,673 issued to Bloomquist (xe2x80x9c""673 patentxe2x80x9d) discloses a dual mode intravenous infusion device with a distal sensor. The dual modes are: controller and pump. The controller does not contribute to the downstream fluid pressure. In the pumping mode, an alarm condition is triggered and the pump ceases operation upon detection of the downstream fluid pressure exceeding a threshold. In the controller mode, fluid pressure downstream is less than fluid pressure upstream under normal operating conditions. The device disclosed in the ""673 patent triggers an alarm when the differential between the fluid pressure downstream from the controller and the fluid pressure upstream from the controller is a null. In other words, the ""673 triggers an alarm when the downstream pressure increases up to, and equals, the upstream pressure. The ""673 patent does not address the issue of detecting overpressurization of a fluid source. Therefore, the ""673 patent does not disclose detection of abnormally high upstream pressure, with or without detection of abnormally high downstream pressure. The ""673 patent also does not disclose detection of a condition in which the difference between the upstream and downstream pressures is outside a predetermined range of acceptable values.
Accordingly, there is a need in the prior art for a system and method that will detect abnormal pressure upstream, downstream, and differentially and, upon detection of such an abnormal pressure, will provide an indication of the abnormal pressure, such as by activating an alarm.
In one embodiment, this invention includes a system for providing an indication of an abnormal fluid pressure upstream of a medicament pump. The system includes: a pressurized source of fluid coupled to the pump inlet via a pump inlet tube; a pump inlet pressure sensor for sensing fluid pressure upstream from the pump; and an abnormal inlet pressure alarm coupled and responsive to the pump inlet pressure sensor. The inlet pressure sensor may be a strain gauge attached to, or incorporated into, the wall of the pump inlet tube.
The system is also capable of providing an indication of an abnormal fluid pressure downstream of the medicament pump. The system may further include: a pump outlet pressure sensor for sensing fluid pressure downstream from the pump; and an abnormal outlet pressure alarm coupled and responsive to the pump outlet pressure sensor. The outlet pressure sensor may be a strain gauge attached to, or incorporated into, the wall of the pump outlet tube.
In addition to monitoring the inlet, or upstream, and the outlet, or downstream, pressures individually, the system includes means for calculating the difference between the upstream and downstream pressures and means for indicating that the calculated difference is outside a predetermined range of acceptable difference pressure values. The components of this system may be adapted to be implanted within a person""s body.
In another embodiment, this invention also includes a method of indicating abnormal fluid pressure upstream of a medicament pump. The method includes the steps of: monitoring the fluid pressure upstream of the pump; and activating an alarm based upon the monitored upstream fluid pressure being outside a predetermined acceptable range of values. This invention further includes a method for indicating abnormal fluid pressure downstream from the medicament pump. This method further includes the steps of: monitoring the fluid pressure downstream from the pump; and activating an abnormal outlet pressure alarm based upon the monitored downstream fluid pressure being outside a predetermined range of acceptable values. Additional steps include: calculating a difference between the upstream pressure and the downstream pressure; and activating an abnormal difference pressure alarm upon the calculated difference pressure being outside a predetermined acceptable range of values.
Also included is a method of indicating abnormal fluid pressure upstream and/or downstream of a peristaltic pump including the following steps: monitoring the fluid pressure upstream of the pump; monitoring the fluid pressure downstream from the pump; calculating a difference between the upstream pressure and the downstream pressure; and activating an abnormal difference pressure alarm upon the calculated difference pressure being outside a predetermined acceptable range of difference pressure values. Additional steps could include: activating an abnormal inlet pressure alarm based upon the monitored upstream fluid pressure being outside a predetermined acceptable range of inlet pressure values; and activating an abnormal outlet pressure alarm based upon the monitored downstream fluid pressure being outside a predetermined acceptable range of outlet values.
In a further embodiment, this invention comprises a medicament pump having a computer-readable medium, such as a random access memory, having computer-executable instructions for processing and providing signals. The computer-executable instructions and signals achieve essentially the same functionality as described above with respect to the method steps.
Each of these embodiments may be used separately or together in various combinations and permutations.